A discussion of “hidden subduction” in orogenic belts

2020 ◽  
Vol 57 (3) ◽  
pp. 418-425
Author(s):  
A.M.C. Şengör ◽  
John F. Dewey
Keyword(s):  
Early Cretaceous ◽  
Sedimentary Cover ◽  
Oceanic Lithosphere ◽  
Early Jurassic ◽  
Unanswered Question ◽  
The North ◽  
Hindu Kush ◽  
Caspian Depression ◽  
Oceanic Basement ◽  
Orogenic Belts

The McKenzie et al. (2019) model concerning the cause of the deep earthquakes in the Hindu Kush region in Asia greatly resembles the hidden subduction model proposed earlier. However, in the case of the Hindu Kush, the age of the disappearance of the Tethyan waters was early Jurassic and the sutures were overlain by early Cretaceous sedimentary cover. The question then becomes how long a “subcutaneous” oceanic lithosphere can survive within a continent. It seems that the “oceanic” basement of the North Caspian Depression has been there since the late Palaeozoic, which is encouraging for the McKenzie et al. model. Whether an already subducted slab can also survive for more than 100 million years attached to its continental continuation remains an unanswered question. In the examples with which we are familiar (eastern Turkey, Apennines, Magrebides, Betic and Rif cordilleras), subducted lithosphere became detached at most 25 million years after collision.

Control of Precambrian-to-Paleozoic orogenic trends on along-strike variations in Early Cretaceous continental rifts of the South Atlantic Ocean

2019 ◽  
Vol 7 (4) ◽  
pp. SH45-SH69 ◽  
Author(s):  
Kyle Reuber ◽  
Paul Mann
Keyword(s):  
Early Cretaceous ◽  
South Atlantic ◽  
Orogenic Belt ◽  
Deep Penetration ◽  
The South ◽  
The North ◽  
Continental Rifts ◽  
Rift Zones ◽  
Seismic Reflection Profiles ◽  
Orogenic Belts

The Early Cretaceous (135–130 Ma) continental rupture of Western Gondwana to form the South American and African plates closely paralleled the elongate trends of Precambrian and Paleozoic orogenic belts. These orogenic belts were produced as a result of the Neoproterozoic convergent and strike-slip assembly of Gondwana that redeformed during later, Paleozoic orogenic events. Continued continental rifting led to the formation of conjugate, South Atlantic volcanic passive margins whose widths vary from 55 to 180 km. Along-strike variations in crustal stretching, as measured from deep-penetration seismic reflection profiles, correlate with parallel and oblique orientations of rifts relative to the trend of the orogenic, basement fabric. Where orogenic fabric trends parallel to the north–south South Atlantic rift direction such as in the Dom Feliciano orogenic belt of Uruguay and Brazil and the Kaoko Uruguay/Brazil and Kaoko orogenic belt of Namibia, we observe narrow (55–90 km) rift zones with modest continental beta factors of 2.5–3.5 because smaller amounts of rifting were needed to stretch the weaker and parallel, orogenic, basement fabric. Where the basement fabric trends near-orthogonally to the north–south South Atlantic rift direction such as in the Salado suture of Southern Uruguay and the Damara Belt of Namibia, we observe wider (185–220 km) rift zones with higher beta factors of 4.3–5 because greater amounts of stretching were needed to rupture the orthogonal, orogenic, basement fabric. The rift-oblique Gariep Belt intersects the South Atlantic continental rupture at an intermediate angle (30°) and exhibits a predicted intermediate beta factor of 4.0. A compilation of published beta factors from 36 other rifted margins worldwide supports the same basement-trend-degree of stretching relationship that we have developed — with rift-parallel margins having lower beta factors in a range of 1.3–3.5 and rift-orthogonal or oblique margins having higher beta factors in a range of 4–8.

Triassic calc-alkaline lamprophyre dykes from the North Qiangtang, central Tibetan Plateau: evidence for a subduction-modified lithospheric mantle

2021 ◽  
pp. 1-14
Author(s):  
Bin Liu ◽  
You-Jun Tang ◽  
Lü-Ya Xing ◽  
Yu Xu ◽  
Shao-Qing Zhao ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Oceanic Lithosphere ◽  
Late Triassic ◽  
The North ◽  
Deep Crust ◽  
Central Tibetan Plateau ◽  
Low Degree ◽  
Peridotite Mantle ◽  
Orogenic Belts ◽  
Isotopic Variations

Abstract Primitive lamprophyres in orogenic belts can provide crucial insights into the nature of the subcontinental lithosphere and the relevant deep crust–mantle interactions. This paper reports a suite of relatively primitive lamprophyre dykes from the North Qiangtang, central Tibetan Plateau. Zircon U–Pb ages of the lamprophyre dykes range from 214 Ma to 218 Ma, with a weighted mean age of 216 ± 1 Ma. Most of the lamprophyre samples are similar in geochemical compositions to typical primitive magmas (e.g. high MgO contents, Mg no. values and Cr, with low FeOt/MgO ratios), although they might have experienced a slightly low degree of olivine crystallization, and they show arc-like trace-element patterns and enriched Sr–Nd isotopic composition ((87Sr/86Sr)i = 0.70538–0.70540, ϵNd(t) = −2.96 to −1.65). Those geochemical and isotopic variations indicate that the lamprophyre dykes originated from partial melting of a phlogopite- and spinel-bearing peridotite mantle modified by subduction-related aqueous fluids. Combining with the other regional studies, we propose that slab subduction might have occurred during Late Triassic time, and the rollback of the oceanic lithosphere induced the lamprophyre magmatism in the central Tibetan Plateau.

Mesozoic thermal history and timing of structural events for the Yukon-Tanana Upland, east-central Alaska: 40Ar/39Ar data from metamorphic and plutonic rocks

2002 ◽  
Vol 39 (6) ◽  
pp. 1013-1051 ◽  
Author(s):  
Cynthia Dusel-Bacon ◽  
Marvin A Lanphere ◽  
Warren D Sharp ◽  
Paul W Layer ◽  
Vicki L Hansen
Keyword(s):  
Early Cretaceous ◽  
Final Stage ◽  
Complex Interaction ◽  
Early Jurassic ◽  
Crustal Thickening ◽  
Late Triassic ◽  
East Central ◽  
The North ◽  
Plutonic Rocks ◽  
Lake George

We present new 40Ar/39Ar ages for hornblende, muscovite, and biotite from metamorphic and plutonic rocks from the Yukon–Tanana Upland, Alaska. Integration of our data with published 40Ar/39Ar, kinematic, and metamorphic pressure (P) and temperature (T) data confirms and refines the complex interaction of metamorphism and tectonism proposed for the region. The oldest metamorphic episode(s) postdates Middle Permian magmatism and predates the intrusion of Late Triassic (215–212 Ma) granitoids into the Fortymile River assemblage (Taylor Mountain assemblage of previous papers). In the eastern Eagle quadrangle, rapid and widespread Early Jurassic cooling is indicated by ~188–186 Ma 40Ar/39Ar plateau ages for hornblende from plutons that intrude the Fortymile River assemblage, and for metamorphic minerals from the Fortymile River assemblage and the structurally underlying Nasina assemblage. We interpret these Early Jurassic ages to represent cooling resulting from northwest-directed contraction that emplaced the Fortymile River assemblage onto the Nasina assemblage to the north as well as the Lake George assemblage to the south. This cooling was the final stage of a continuum of subduction-related contraction that produced crustal thickening, intermediate- to high-P metamorphism within both the Fortymile River assemblage and the structurally underlying Lake George assemblage, and Late Triassic and Early Jurassic plutonism in the Fortymile River and Nasina assemblages. Although a few metamorphic samples from the Lake George assemblage yield Jurassic 40Ar/39Ar cooling ages, most yield Early Cretaceous 40Ar/39Ar ages: hornblende ~135–115 Ma, and muscovite and biotite ~110–108 Ma. We interpret the Early Cretaceous metamorphic cooling, in most areas, to have resulted from regional extension and exhumation of the lower plate, previously tectonically thickened during Early Jurassic and older convergence.

scholarly journals THE INTRAPLATE VOLCANO-TECTONIC ACTIVITY IN NORTH-EASTERN AND SOUTH SECTORS OF THE PACIFIC LITHOSPHERIC PLATES WITH THE CONNECTION OF THE CHANGE OF ITS RELATIVE MOTION

2021 ◽  
Vol 49 (4) ◽  
pp. 102-127
Author(s):  
E. G. Mirlin ◽  
T. I. Lygina ◽  
E. I. Chesalova
Keyword(s):  
Relative Motion ◽  
Sedimentary Cover ◽  
Oceanic Lithosphere ◽  
Pacific Plate ◽  
Fault System ◽  
Tectonic Activity ◽  
The North ◽  
The Pacific ◽  
North Eastern ◽  
Absolute Age

The analysis of altimetric data in combination with bathymetry and gravimetry materials in the north-eastern and southern sectors of the Pacific Ocean, as well as detailed data on the underwater relief, the structure of the sedimentary cover, the composition and absolute age of basalts obtained within the area of domestic geological exploration for ferromanganese nodules (the Clarion-Clipperton zone) is carried out. Structural trends formed by local cone-shaped local structures of presumably volcanic nature, grouped along transform faults belonging to various stages of the kinematics of the Pacific Plate, have been traced in the structure of the oceanic lithosphere at various scale levels. The first trend corresponds to the extension of the fault system corresponding to the spreading system on the crest of the East Pacific rise before the restructuring of its planned geometry in the Paleocene-Eocene, the second coincides with their extension after the change in the relative movement of the Pacific Plate. The trends are characterized by planned disagreement, and an increase in the number of seamounts is observed in the areas of their intersection. Within the area of detailed studies, obvious signs of volcanic-tectonic activity were revealed: high dissection of the underwater relief, hills of different heights with steep slopes, whose volcanic nature is confirmed by differentiated basalts raised from their slopes, the absolute age of which indicates the multistage outpourings that occurred in an intraplate environment. The angular velocity of rotation of the spreading axis and the linear velocity of its advance with changes in the kinematics of the Pacific plate are estimated and possible reasons for changes in its relative motion are considered. An improved scheme of adaptation of the spreading zone to a change in the direction of relative plate movement is proposed, acc0ording to which an essential factor of intraplate volcanic-tectonic activity is the relaxation of stresses in the plate caused by external influence on it.

scholarly journals U-Pb geochronology and paleogeography of the Valanginian–Hauterivian Neuquén Basin: Implications for Gondwana-scale source areas

Geosphere ◽  
2020 ◽  
Author(s):  
E. Schwarz ◽  
E.S. Finzel ◽  
G.D. Veiga ◽  
C.W. Rapela ◽  
C. Echevarria ◽  
...  
Keyword(s):  
Delivery System ◽  
Early Cretaceous ◽  
Detrital Zircon ◽  
Sedimentary Basins ◽  
Early Jurassic ◽  
Source Areas ◽  
Base Level ◽  
The North ◽  
Neuquen Basin ◽  
Neuquén Basin

Sedimentary basins located at the margins of continents act as the final base level for con­tinental-scale catchments that are sometimes located thousands of kilometers away from the basin, and this condition of exceptionally long sediment transfer zones is probably reinforced in supercontinents, such as Gondwana. One of the most prominent marine basins in southwestern Gondwana during the Jurassic and Early Cretaceous was the Neuquén Basin (west-central Argentina), but its role as a sediment repository of far-flung source areas has not been extensively considered. This contribution provides the first detailed detrital-zircon U-Pb geochronology of the Valanginian–Hauterivian Pilmatué Member of the Agrio Formation, which is combined with sedimentology and paleogeographic reconstructions of the unit within the Neuquén Basin for a better understanding of the fluvial delivery systems. Our detrital-zircon signatures suggest that Triassic–Permian zircon populations were probably sourced from the adjacent western sector of the North Patagonian Massif, whereas Early Jurassic, Cambrian, Ordovician, and Proterozoic grains were most likely derived from farther east, in the eastern sector of the North Patagonian Massif, as well as presently remote terranes such as the Saldania Belt in southern Africa. We thus propose a Valanginian–Hauterivian longitudinal delivery system that, starting in the mid-continent region of southwestern Gondwana and by effective sorting, was bringing fine-grained or finer caliber sand to the Neuquén Basin shoreline. This delivery system was probably active (though not necessarily continuously) from Early Jurassic to Early Cretaceous until finally coming to an end during the opening of the South Atlantic Ocean in the latest Early Cretaceous.

scholarly journals Sedimentary and Source-to-Sink Evolution of Intracontinental Basins: Implications for tectonic and Climate Evolution in the Late Mesozoic (Southern Junggar Basin, NW China)

2022 ◽  
Vol 9 ◽  
Author(s):  
Xutong Guan ◽  
Chaodong Wu ◽  
Xuecai Zhang ◽  
Weiwei Jia ◽  
Wei Zhang
Keyword(s):  
Early Cretaceous ◽  
Late Jurassic ◽  
Junggar Basin ◽  
Orogenic Belt ◽  
Alluvial Fan ◽  
Late Mesozoic ◽  
The North ◽  
Source To Sink ◽  
Tianshan Orogenic Belt ◽  
Orogenic Belts

Sedimentary investigations, petrography, heavy mineral and conglomerate component analyses, and detrital zircon U-Pb geochronology were conducted to reconstruct the sedimentary and source-to-sink evolution of the Southern Junggar Basin, an intracontinental basin in the late Mesozoic. A paludal deltaic environment evolved into a fluvial environment, and abruptly prograded into alluvial fan and aeolian environments in the Late Jurassic, which was replaced by fan deltaic and lacustrine environments in the Early Cretaceous. Three source-to-sink systems were identified, according to different source-to-sink system features. In the northern piedmont of the Tianshan Orogenic Belt, the North Tianshan Orogenic Belt mainly provided sediments in the Late Jurassic. The North Tianshan and Central Tianshan Orogenic Belt both supplied sediments in the Early Cretaceous. In the northern piedmont of the Bogda Orogenic Belt, the Bogda Orogenic Belt was constantly the primary provenance, and the Tianshan Orogenic Belt also provided sediments. Sediment recycling occurred in the basin margin in the Late Jurassic and more metamorphic rocks were denudated in the Early Cretaceous. The source-to-sink system shrank in the Late Jurassic and expanded in the Early Cretaceous. This source-to-sink evolution and the conglomerates in the Kalazha Formation with seismite structures responded to the aridification in the Late Jurassic, the uplift of the Bogda and Tianshan Orogenic Belts in the Late Jurassic, and the exhumation of the Bogda and Tianshan Orogenic Belts in the Early Cretaceous.

Early Cretaceous extensional allochthons in the Taihang Shan associated with destruction of the North China Craton

2021 ◽  
pp. 104933
Author(s):  
Wuke Chen ◽  
Yi Liufu ◽  
Lei Wu ◽  
Chenyu Zhang ◽  
Hongwei Zhang ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
North China Craton ◽  
North China ◽  
The North

New multituberculate mammal from the Early Cretaceous of eastern North America

2013 ◽  
Vol 50 (3) ◽  
pp. 315-323 ◽  
Author(s):  
Richard L. Cifelli ◽  
Cynthia L. Gordon ◽  
Thomas R. Lipka
Keyword(s):  
North America ◽  
Iberian Peninsula ◽  
Early Cretaceous ◽  
North American ◽  
Lower Cretaceous ◽  
Late Jurassic ◽  
Relative Length ◽  
Central Position ◽  
Eastern North America ◽  
The North

Multituberculates, though among the most commonly encountered mammalian fossils of the Mesozoic, are poorly known from the North American Early Cretaceous, with only one taxon named to date. Herein we describe Argillomys marylandensis, gen. et sp. nov., from the Early Cretaceous of Maryland, based on an isolated M2. Argillomys represents the second mammal known from the Arundel Clay facies of the Patuxent Formation (Lower Cretaceous: Aptian). Though distinctive in its combination of characters (e.g., enamel ornamentation consisting of ribs and grooves only, cusp formula 2:4, presence of distinct cusp on anterobuccal ridge, enlargement of second cusp on buccal row, central position of ultimate cusp in lingual row, great relative length), the broader affinities of Argillomys cannot be established because of non-representation of the antemolar dentition. Based on lack of apomorphies commonly seen among Cimolodonta (e.g., three or more cusps present in buccal row, fusion of cusps in lingual row, cusps strongly pyramidal and separated by narrow grooves), we provisionally regard Argillomys as a multituberculate of “plagiaulacidan” grade. Intriguingly, it is comparable in certain respects to some unnamed Paulchoffatiidae, a family otherwise known from the Late Jurassic – Early Cretaceous of the Iberian Peninsula.

The Currently Earliest Angiosperm Fruit from the Jurassic of North America

2021 ◽  
Vol 2 (4) ◽  
Author(s):  
Xin Wang
Keyword(s):  
North America ◽  
Early Cretaceous ◽  
Middle Jurassic ◽  
Early Evolution ◽  
The North ◽  
Plant Group ◽  
Ecological Radiation ◽  
Origin Of Angiosperms ◽  
Crucial Test

Angiosperms are the single most important plant group in the current ecosystem. However, little is known about the origin and early evolution of angiosperms. Jurassic and earlier traces of angiosperms have been claimed multiple times from Europe and Asia, but reluctance to accept these records remains. To test the truthfulness of these claims, palaeobotanical records from continents other than Europe and Asia constitute a crucial test. Here I document a new angiosperm fruit, Dilcherifructus mexicana gen. et sp. nov, from the Middle Jurassic of Mexico. Its Jurassic age suggests that origin of angiosperms is much earlier than widely accepted, while its occurrence in the North America indicates that angiosperms were already widespread in the Jurassic, although they were still far away from their ecological radiation, which started in the Early Cretaceous.

Sign in / Sign up

Export Citation Format

Share Document